1. Field of the Invention
The invention relates to a personal computer system where each external mass storage devices has a system boot-up function, equivalent to a floppy disk, used to boot-up the system.
2. Description of the Related Art
In recent years, personal computers have become widespread and are commonly used in both home and office environments. In order to facilitate this growth in the use of computers, the connection of various external devices to the computer via interface boards has become quite common.
One external device often connected to personal computers is the external mass storage device. Common devices used for the external mass storage device include Hard Disk Drives (HDD), Magneto-Optic recording and playback systems (MO), and the like.
These external mass storage devices may be utilized in various ways suitable for respective devices. For instance, the hard disk device and magneto-optic recording and playback device have large storage capacity, and thus are suitable for storing a plurality of application programs and/or a large amount of data. Therefore, in a personal computer system including these external mass storage devices, the devices are selectively used.
The system boot-up of a personal computer is carried out as following. For example, in a personal computer of the kind which incorporates a floppy disk drive and a hard disk drive and employs MS-DOS (an operating system developed by MICROSOFT CORPORATION, in USA; a registered Trademark) as an operating system (OS), at first, an IPL loader (Initial Program Loader) stored in a system ROM of the personal computer is started by turning on the power supply or by resetting the system. The IPL loader reads the IPL (initial load program) into an internal memory of the personal computer from the floppy disk drive or the hard disk drive (the floppy disk drive has priority) through a standard BIOS, thereby the control transfers to the IPL, and the IPL reads the MS-DOS as the OS into the memory from the floppy disk drive or the hard disk drive (the floppy disk drive has priority), then the control transfers to MS-DOS, and consequently MS-DOS is started.
When MS-DOS is in a boot-up state, the external mass storage device described above can be placed under the control of the MS-DOS by either of the following methods.
The first method is the one in which a device driver (a program for placing the external device under the control of OS) corresponding to the external mass storage device is read from the floppy disk or the hard disk drive to control the external mass storage device by this device driver.
The second method is the one in which, in a case for example, where a magneto-optic recording playback device is used as an external mass storage device, in order to handle this magneto-optic recording playback device in a pseudo fashion as a hard disk drive, the system standard BIOS stored in the system ROM of the personal computer is replaced with a BIOS, newly provided on an interface board, so that a command for the hard disk drive is converted into a command for the magneto-optic recording playback device.
The first method is a most simple and ordinary method for connecting the external mass storage device with the personal computer. However, reading of the device driver is required to be carried out from a device (FDD or HDD) other than the external mass storage device before the external mass storage device is placed under the control of said OS (MS-DOS), notwithstanding, that the hardware (standard BIOS) of the personal computer is set so that the OS is read from the FDD or HDD by all means immediately after turning on the power supply or resetting the system, so that the system boot-up can not be performed from the external mass storage device itself.
In addition, since the second method recognizes the external mass storage device as a hard disk drive in a pseudo manner, the system boot-up can be performed by reading OS from this external mass storage device; however, this can not avoid a restriction for the hard disk drive in the OS (MS-DOS) that the external mass storage device after exchanging of media is not recognized as a formal external mass storage device. Due to this restriction, for example, in a case where a plurality of magneto-optic recording playback devices are media-exchanged and used as a proper external mass storage device, if the media exchange is forced as it is, normal access can not be performed and the external mass storage device and data therein tend to be broken. As a result, restarting must be done by resetting the system when the media exchange is performed after all. This arrangement therefore can not exhibit the ability to exchange media that is an advantage of the magneto-optic recording playback device.